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Field-Ionization Based Electrical Space Ion Thruster Using a Permeable Substrate

This invention describes a dual propulsion system with a single-propellant source used for either a high specific impulse mode (an ion-thruster mode) or a low specific impulse mode (a cold-gas thruster mode). The high specific impulse mode utilizes a miniaturized positive-ion field-ionization chamber which consists of a grid or other permeable substrate material infused with properly oriented carbon nanotubes through which the propellant flows. Field-electron emission from a neutralizer, such as a carbon nanotube array neutralizer, positioned downstream of accelerator grids may be used for ion neutralization. The low specific impulse mode utilizes conventional supersonic nozzles.

When compared to conventional electron-bombardment-ionization, the invention’s chamber is more compact and its field ionization provides only singly-charged positive ions. The positive ions generated are electrostatically repelled from the ionizer surface because it is an anode, obviating the ion-impingement cathode damage that has plagued prior-art ionizers. This translates into longer lifetime. Further, no magnets are required and no extra propellant is wasted in neutralization when electron-field emission neutralizers are used. The ionization chamber’s compactness enables ion thruster applications to small satellites.

Nano- and pico-satellite applications require high specific impulses for orbit maintenance and low specific impulses for orbit maneuvers. The disclosure’s miniaturized ion thruster embodiment is useful for small satellites because the physical depth of the ionizer dimension may be decreased by as much as 80% (not the cross section) over the present state of the art for the same thruster performance. The use of a single propellant such as argon for both propulsion modes is both efficient and practical.

Patent Number: 
US 9,194,379
Technology Type(s): 
Patent Status: 
Patent Issue Date: 
November 24, 2015
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